Telephone-circuit



(No Model.)

G H. BLISS.

TELEPHONE GIRGUIT. No. 259,286 Patented June 13, 1882,.

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in the employment of one or more lines, each ex- 1 b, the said line at being normally insulated or I00 UNITED STATES ATENT FFICE.

GEORGE H. BLISS, OF PITTSFIELD, MASSACHUSETTS.

TELEPHONE-CIRCUIT.

SPECIFICATION forming part of Letters Patent No. 259,286, dated June 13, 1882.

Application filed November 12, 1881.

To all whom it may concern:

Be it known that I, GEORGE E. Buss, of Pittsfield, county of Berkshire, State of Massachusetts, have invented an Improvement in Telephone-Circuits, of which the following description, in connection with the accompanying drawing, is a specification.

My invention relates to telephone-circuits, and has for its object to enable the various subscribers circuits connected with a central office to be connected with those of another central office by a metallic circuit, so that communication can be carried on between the subscribers of the two exchanges without disturbance by induction from the parallel lines carried upon the same poles or included in the same cables in the space between the said central offices.

It is well known that by the employment of pro perly-arran ged metallic circuits the disturbances commonly caused by induction from parallel lines may be wholly avoided; but this arran gement generally involves the employment of a metal circuit to the extreme end of the line, although the portion near the said end may not be exposed to disturbance. Thus,for example, in the case of central offices in two difierent cities, the different subscribers circuits branching from the same central office are not generally exposed ,-to inductive disturbance sufliciently to interfere with their proper working, and consequently grounded circuits are employed, as they are less expensive than the metallic circuits arranged to neutralize such disturbances. When, however, the subscribers of one central oftice desire to talk with those of the other central office, the currents have to traverse the space between the two central offices, through which the lines are carried on the same poles with telegraph-lines or other telephone-lines, and are consequently exposed to disturbances which would seriously interfere with the telephonic communication unless means were employed to neutralize their effect.

Plans have been proposed for transmitting the electric impulses from a metallic to an independent grounded circuit; but the present invention has for its object to enable one continuous circuit to be employed 5 and it consists (No model.)

tending from the central office into a large number of the subscribers stations, the said line being provided with suitable branches when needed to enter the different stations, and being normally open. Suitable switches are provided at each of the said offices to connect the subscribersline with the said line, thus forming a metallic circuit having its ends in the central office, where they can be connected with the ends of the metallic circuit extending to the other central office, in which the other subscribers line may be similarly connected, making a metallic circuit throughout; or, if desired, at one of the central offices one end of the metallic circuit connecting the offices may be grounded and the other end connected with the subscribers line, which will then be grounded at the subscribers station, in the usual manner.

The drawing shows a diagram of the circuits connected with two central offices of two exchanges, themselves connected by a metallic circuit. The two central oflices are represented at A B, each having the usual subscribers lines, a b, radiating therefrom, and each passing through one or more subscribers stations to the ground. These subscribers lines I) are not generally exposed to serious inductive disturbance, so that for the purpose of communicating between the different subscribers of one exchange, as that at A, grounded circuits are sufficient. When, however, a subscriber of one exchange, as A, desires to communicate with a subscriber of the other exchange, B, the currents have to traverse the space between A and B, in which the circuit is exposed to serious disturbance. For the purpose of avoiding this disturbance the central offices A B are connected by one or more metallic circuits, one of which is shown at 0, arranged in the wellknown manner to neutralize the effects of induction between it and other parallel lines passing over the route between the said central offices, such an arrangement being fully described in English Patent N 0. 1,341 of 1877. Each central office is also provided with one or more wires, d, passing through or having branches entering a large number of subscribers stations on the various subscribers lines a open in the said subscribers stations. Each of the two portions of the metallic circuit 0, connecting the central offices, is arranged to be connected with one of the horizontal or circuit-connecting strips of the switch-board, and the wires 01 are connected with the vertical or line strips of the switch-board; and in each subscribers office a suitable switch, f, is employed to connect that portion of the subscribers line between the said station and the central office with the said line (1 whenever communication is desired with a member of the distant exchange.

In the drawing, a subscribers station, 2, of the central office A is shown as connected for communication with the subscribers station 3 of the exchange B, the switchf at each of the said stations being turned to connect the subscribers wires entering the said stations with the wires d. At the central office A the subscribers wire a of station 2 is connected in the usual manner with the horizontal strip of the switch-board connected with one portion of the metallic circuit a, while the wired is connected by the said switch-board with the other portion of the said circuit; and in the central oftice B the subscribers line b and wire (1, connected at station 3, are respectively connected with the strips of the switch-board connected with the two portions of the metallic circuit 0', so that a complete metallic circuit is afforded between the stations 2 and 3, as indicated by the arrows, it including both parts of the metallic circuit 0 between the ofifices A and B.

The wires (1 may, if desired, be permanently connected with one portion of the metallic circuit c at the central offices, the said metallic circuit being thus essentially extended into all the subscribers stations, so that the subscribers circuit can be at onceincluded in the said metallic circuit when desired. It is obvious that any number of exchanges can be connected in this manner.

I claim In a telephone-exchange system, two central otfices connected bya metallic circuit arranged to annul inductive disturbances, each office having connected with it subscribers circuits and one or more lines extended into a large number of subscribers stations, combined with means to connect the said line with the subscribers circuit at the subscribers station, and means to connect the said line and subscribers circuit with the two portions of the metallic circuit connecting the central offices, substantially as and for the purpose described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

GEORGE H. BLISS.

WVitnesses:

JOHN F. VAN DEUSEN, HOMER, H. BIGKNELL. 

